REDUCTION OF AIR ION MOBILITY TO STANDARD CONDITIONS

The Langevin rule of the reduction of air ion mobility is adequate in case of zero-size ions. An alternative is the Stokes-Millikan equation that is adequate in the limit of macroscopic charged particles. The t emperature variation of air ion mobility predicted by the Stokes-Milli kan equation radically contradicts the Langevin rule. The temperature and pressure variation of air ion mobility is examined by using a new semiempirical model that describes the transition from the kinetic the ory to the Stokes-Millikan equation. The model is valid in full mobili ty range. It allows to calculate at first the size of an ion according to the measured mobility and then the standard mobility according to the size. The ascent of the temperature-mobility curve on a logarithmi c chart approaches the Langevin value of 1 only at very high mobilitie s not found in the atmosphere. The value of the ascent is 0.6 in the c ase of small ions of the mobility of 1.5 cm(2) V-1 s(-1) which brings about a considerable error when using the Langevin rule. It is recomme nded to store the natural values of the mobility in databases together with the values of temperature and pressure and to definitely indicat e the method when the reduced mobilities are presented in publications .